Method for preparing large-area structural chromogenic pattern by ink-jet printing and anti-counterfeiting method based on structural color change

Abstract

A method for preparing a large-area structural chromogenic pattern by ink-jet printing, a structural chromogenic pattern obtained by the method, and an anti-counterfeiting method based on a structural color change. A dispersion liquid containing mono-disperse colloidal microspheres with high index of refraction is printed onto a piece of paper by using an ink-jet printer, and nano-microspheres are arranged and assembled on the paper to obtain a micro-structure having the features of being ordered from a short distance and disordered from a long distance. A pretty structural color can be observed by means of the interaction of the structure with light, thus displaying a pattern, changing the angle of observation, changing the brightness of the structural color, and hiding and displaying the pattern. The method is simple and convenient, is widely applicable, and can achieve the preparation and anti-counterfeiting of a large-area structural color without external stimulation.

The invention claimed is: 
     
       1. A method for preparing a structural chromogenic pattern by ink-jet printing, comprising:
 (1) preparing a plurality of inks including a first ink and a second ink, each ink containing mono-disperse colloidal microspheres having a refractive index greater than 2, wherein the first ink contains a first mono-disperse colloidal microspheres having a first average particle diameter, and the second ink contains a second mono-disperse colloidal microspheres having a second average particle diameter, and the first average particle diameter differs from the second average particle diameter, wherein the first mono-disperse colloidal microspheres and the second mono-disperse colloidal microspheres are made of a same material; 
 (2) designing a pattern having two or more different colors through computer software; and 
 (3) using the plurality of inks prepared in step (1) to print the pattern designed in step (2) on paper through ink-jet printing technology to obtain the structural chromogenic pattern. 
 
     
     
       2. The method according to  claim 1 , wherein the first mono-disperse colloidal microspheres and the second mono-disperse colloidal microspheres are made of cadmium sulfide, cuprous oxide, titanium dioxide, zinc sulfide, or zinc oxide, and the first average particle diameter and the second average particle diameter are in a range of 90 nm to 400 nm. 
     
     
       3. The method according to  claim 1 , wherein, in the first ink or the second ink, a content of the mono-disperse colloidal microspheres is 5 wt % to 20 wt %, a content of an additive is 5 wt % to 15 wt %, a content of ethanol is 8 wt % to 20 wt %, a content of the glycerol is 1 wt % to 5 wt %, a content of a surfactant is 2 wt % to 5 wt %, a content of a defoaming agent is 0.1 wt % to 0.2 wt %, a content of an adhesive is 1 wt % to 4 wt %, a content of a pH regulator is 2 wt % to 4 wt %, and the balance is the deionized water, wherein the additive is an organic solvent having a boiling point higher than 180° C. 
     
     
       4. The method according to  claim 3 , wherein the additive is ethylene glycol, diethylene glycol, or formamide. 
     
     
       5. The method according to  claim 3 , wherein the surfactant is OP-10 or polyvinylpyrrolidone. 
     
     
       6. The method according to  claim 3 , wherein the defoaming agent is tributyl phosphate. 
     
     
       7. The method according to  claim 3 , wherein the adhesive is polyvinyl alcohol, polyurethane resin, or acrylic resin. 
     
     
       8. The method according to  claim 3 , wherein the pH regulator is triethanolamine, diethanolamine, or ethanolamine. 
     
     
       9. The method according to  claim 3 , wherein the paper is coated paper, resin coated photo paper, and high gloss photographic paper. 
     
     
       10. The large-area structural chromogenic pattern on paper obtained by the method according to  claim 1 . 
     
     
       11. A method for anti-counterfeiting, comprising:
 printing the structural chromogenic pattern according to the method of  claim 1 ; and 
 viewing the structural chromogenic pattern with a vertical incident angle of less than or equal to 30°. 
 
     
     
       12. The method for anti-counterfeiting according to  claim 11 , wherein the structural chromogenic pattern is a matrix code and the observing step is carrying out using a scanning device. 
     
     
       13. The method according to  claim 1 , wherein the first ink is prepared by:
 mixing the first mono-disperse colloidal microspheres, an additive that is an organic solvent with a boiling point greater than 180° C., ethanol, glycerol, surfactant, a defoaming agent, an adhesive, a pH regulator and deionized water to form a mixture; and 
 performing ultrasonic dispersion on the mixture to obtain a stable solution as the first ink.